This volume offers a unique collection of articles investigating the often neglected phenomenon of parentheticals, which are commonly seen as expressions interrupting the linear structure of a host utterance, but lacking a structural relation to it. The book provides an up-to-date introduction to the subject, as well as a range of research articles addressing questions including the syntactic link between parenthetical and frame utterance, the relation between syntactic and prosodic form, the usage and interpretation of parentheticals, and many more. It embraces research findings from different European languages (English, German, Dutch, Romance) and covers an array of forms of syntactic interpolations (from one-word parentheticals to clausal) and a range of methodologies, including empirical research, corpus research, and theoretical analyses. The collection underlines the importance of an interdisciplinary approach to a multi-faceted phenomenon such as parentheticals.